Ignition system for low-voltage ignition in condenser discharge sparking plugs



May 15, 1956 w. B. SMITS 2,745,989

' IGNITION SYSTEM FOR LOW-VOLTAGE IGNITION IN CONDENSER DISCHARGE SPARKING PLUGS Filed May 15 1951 J s 4 mm W in INVENTOR M725 55y -sx x/vza,

BY 2mm ATTORNEY United States Patent IGNITION SYSTEM FOR LOW-VOLTAGE IGNITION IN CONDENSER DISCHARGE SPARKENG PLUGS Wijtze Beije Smits, Voorhurg, Netherlands, assignor to Smitsvonk N. V., Rijswijk, Netherlands Application May 15, 1951, Serial No. 226,390

1 Claim. (Cl. 315-183) This invention relates to a low-voltage ignition system for gapless sparking plugs with condenser discharge. For low-voltage ignition with condenser discharge use is made of a transformer which is fed, for example, from a 6 to 12 volt battery and in which the opening of a circuit-breaker causes current impulses of, for example, 2000 to 3000 volts to be induced in the secondary winding. These current impulses are pulsating, and their course is approximately that of a sine curve. If to this coil one merely connects a condenser, the course of the voltage curve will be improved, but it will assurne the same character of the sine curve as the coil itself. The condenser becomes charged and will discharge in the coil. It is therefore necessary either to disconnect the condenser at the highest point of the sine curve at a sutficient distance or to connect a direct current valve in series between the coil and the con denser. If the frequency is substantially constant, the condenser can be charged by means of a movable circuit-breaker. If, however, as with internal combustion engines, the number of revolutions and consequently the number of interruptions of the primary winding is largely variable, such circuit-breakers, owing to their inertia, tend to produce resonance effects, so that there will be moments when the condenser may be completely discharged or even be negatively charged. Irrespective of the fact that the mechanically moving parts are readily susceptible to breakage, this system also has other disadvantages, such as bad contacting and lack of noiselessness.

If use is made, for example, of a rectifier tube with selenium cells or the like, all these drawbacks are obviated. The advantage of such a tube is, however, counterbalanced by the very high cost at a voltage of 2000 to 3000. Moreover, such tubes always have some electric leakage, owing to which the condenser would be gradually discharged.

In order to obviate these drawbacks, the present invention makes use of a short tube and a small sparking gap. According to the invention, the element supplying the current impulses, for example, the secondary winding of a transformer, is connected in series with a rectifier element and a sparking gap arrangement, this circuit comprising a condenser connected in parallel, which is connected on the one hand to the pole or poles of one or more low-voltage sparking plugs and on the other hand to earth.

Also, according to the present invention the rectifier element and the sparking gap arrangement can be replaced by an element for determining the breaking down voltage i. e. an element which contains a space filled with an inert gas and in which two electrodes are provided, one of which electrodes has an active surface many times larger than that of the other electrode. The position of these electrodes relative to each other is that of a polarized sparking gap. Such an element may act as a rectifier and at the same time become conductive at a certain voltage.

The invention is explained more in detail by two embodiments given by way of example with reference to the accompanying drawing.

in Figure 1, the numeral 1 designates the secondary winding of a transformer in which current impulses are produced in known manner. The secondary Winding 1 is connected on the one hand to a rectifier element 2 connected in series with a sparking gap 3 and on the other hand to the earth 6. Behind the sparking gap 3 there is disposed, in parallel with the winding 1, a discharging condenser 4 which after passing a distributor discharges through sparking plugs 7. As long as current in the winding 1 increases, a current will flow through the rectifier element 2, while at a given voltage value the sparking gap will break down and the condenser 4 will become discharged. The element 2 and the sparking gap 3 are so adjusted with respect to each other that the negative peak of the voltage value of the dying out of the coil is counterbalanced by the element 2. The charged condenser cannot discharge again, because the open sparking gap 3 has an infinite resistance.

Owing to this connection and adjustment of the sparking gap, a rectifier tube of about 1000 to 1500 volts instead of 2000 to 3000 volts is sufficient. The cost of such a short tube amounts to only 60 per cent of that of a long tube, so that a considerable saving is obtained, while the cost of a sparking gap is very low.

In Figure 2, the numeral 1 designates the secondary Winding of a transformer, in which current impulses are generated in known manner. The secondary Winding 1 is connected on the one hand to an element 2 as described above for determining the breaking down voltage and on the other hand to the earth 6. Behind the element 2 there has been arranged, in parallel with the winding 1, a discharging condenser 4, which after passing a distributor discharges through the sparking plugs 7. When the current in the winding 1 increases, the element 2 will break down at a certain voltage value and the condenser 4 will become charged. The element 2 is so adjusted that the negative peak of the voltage value of the dying out of the coil is counterbalanced by the element 2. The charged condenser cannot discharge again, because the element 2 has an infinite resistance.

I claim:

An ignition system for low voltage spark plugs capable of being fired on a condenser discharge, a condenser, means for supplying current impulses of predetermined voltage to fully charge said condenser, a rectifier having a breakdown voltage of less than said predetermined voltage series connected between said condenser and said charging means, a spark gap series connected with said rectifier whereby dischrge of the condenser through the charging circuit is prevented and at least one low voltage spark plug connected in the discharge path of said condenser.

References Cited in the file of this patent UNITED STATES PATENTS 791,856 Apple June 6, 1905 2,030,228 Randolph Feb. 11, 1936 2,203,579 Randolph June 4, 1940 2,543,371 McNulty Feb. 27, 1951 2,551,101 Debenham May 1, 1951 2,571,788 Tognala Oct. 16, 1951 

